We propose to develop membrane-cell fusion methods to test for thyroid stimulating immunoglobulins (TSI) and for cell-mediated cytotoxicity: 1) Using TSH-receptors from fat or thyroid cell membranes fused into cultured mouse tumor cells, develop sensitive TSH and TSI assay, measuring cAMP response. 2) Characterize biochemically the thyroglobulin-binding protein(s) in human eye muscle; transfer this material to lipid vesicles, and fuse the latter to 111In-cultured tumor cells. Test cytotoxicity of recipient cells exposed to human lymphocytes of Graves' disease patients. We will conduct a 12 year follow-up review of the results of orbital radiotherapy in 200 patients with Graves' ophthalmopathy.